Which one you would do it?
I now have a 10bolt rear end and I will some day rebuilt it and bolt something to strengthen it, and gears and posi.
With a budget would 9bolts rebuilded or 10 rebuilded be more reasonable for my use. I am a daily driver, do burnouts sometimes but seldom go to drag strip(remember: we don't have as much traction here as you do there). I also want to do some road racing and (maybe) autocross.
I know 9bolt would be stronger but would it be woth it to swap rear end in which it is very hard to find parts here. Should I just add stregnth to my 10bolts and save that money to my engine?

 

If you currently have a 10 bolt I would just have it rebuilt with quality parts and use that. It should stand up quite well to what you said you wanted to do with it.